Updating the RRFS GRIB2 variable handle for "MSTAV"

[jaymes-kenyon]

A previous commit to the UPP repository (NOAA-EMC/UPP@83e59b5) resulted in a change to the RRFS GRIB2 variable handle for soil moisture availability (MSTAV). As a result of this change, Python graphics are failing in RRFS-B. Running an "ncl_filedump" on a recent RRFS-B GRIB2 file indicates that the new variable handle is "MSTAV_P0_L106_GLC0". This update to pygraf has been successfully used in a RRFS CONUS 3-km retro on Hera.

[cshartsough]

Thanks for putting this together. I should still add something down the road to exit more gracefully when the needed fields for the firewx or other calcs aren't available.

[jaymes-kenyon]

Thanks, @cshartsough. BTW, I do not have write access here; can someone click the "merge" button? Then, I'll make a separate PR in ufs-srweather-app to update the pygraf hash.